Dipoles Definition and 107 Threads

Hi, In quantum optics, the interaction between light and atoms is described by a Hamiltonian of the form d.E where d is the dipole moment of the atom. The picture given is basically that this is a vector and we take the the dot product with this and the electric field vector (whose direction...

Homework Statement THE ANSWER IS CHomework Equations None given. Pondering: E=(1/(2(pi)εnaught))(σ/z^3) p=qd U=-p dotprod EThe Attempt at a Solution We have attempted many variations of the above equations to try and find the answer. We are just seeking a point in the right direction as we...

Homework Statement Imagine that all the molecular dipoles in a cup of water could be made to point down. Calculate the magnitude of the resulting surface charge density at the upper surface of the water, and express it in electrons per square centimeter. Homework Equations The...

I'm given two magnetic dipoles on the z-axis with a separation of a distance L. I need to find the fields produced by the individual dipoles at a point on the x-axis in terms of x. This problem is driving me nuts. I've drawn a diagram with the radial vector going from the z-point to the...

(All the variables are vectors, I just didn't feel like fumbling around with the LateX code to make them vectors. Its late and I'm tired a lazy!) Homework Statement (This is paraphrased) There are two dipoles with arbitrary direction to each other. You know the energy between the dipoles is...

Homework Statement In the lectures, we considered a dipole, made of two charges ±q at a separation d. Using Dirac's δ function, write the charge density for this dipole. Evaluate the charge (monopole moment), dipole moment, and quadrupole moments Q, p, and Qij in the multipole expansion...

Image of the problem: It should be very straightforward: derivate p twice and insert it into the equation. I can do all that, but what is the R̅ vector supposed to be? I've read the literature, but it uses a different formula (that I'm not allowed to have with me to the exam) and it never...

Homework Statement We have the setup shown in the figure (see http://cl.ly/JGDDfigure). It rotates with angular velocity ω counter clockwise. ¿Power radiated by the system? (Sorry if it's not the correct translation -- Potencia radiada in spanish). Homework Equations...

Okay. So my assignment is due in an hour and I'm stuck on this last question. If I can get some help, I would greatly appreciate it. So the problem reads: The electric field of a dipole can be calculated by assuming the positive charge q is at z = a/2 and the negative charge -q is at z =...

My question is at the bottom of this post PREAMBLE: If a dipole is turned by an angle θ (in a uniform electric field) then the torque applied on the dipole by the electric field will be: τ = 2.q.a.E.sin(-θ) = -2.q.a.E.sin(θ) with the negative sign referring to it being a "restoring" torque...

Homework Statement An electric dipole consists of 2.0 g spheres charged to 5.0 nC (positive and negative) at the ends of a 12 cm long massless rod. The dipole rotates on a frictionless pivot at its center. The dipole is held perpendicular to a uniform electric field with field strength...

Suppose you have an electric dipole centered at the origin and aligned with the z-axis. If you place a test charge somewhere in the x-y plane, you can show that the force on the dipole by the charge cancels to be zero, yet the dipole still seems to exert a force on the charge... If this is...

Greetings In order to make a mathematical model of the forces that act on a mechanism, I need to use the formula for the force between two magnetic dipoles. It would have to be a complete formula, that should take into consideration, aside magnetic moment and environment permeability...

Homework Statement Two identical dipoles, each of charge q and separation a, are a distance x apart as shown in Fig. By considering forces between pairs of charges in the different dipoles, calculate the net force between the dipoles. (a) Show that, in the limit a<<x, the force has a magnitude...

Homework Statement A point charge Q is distance r from the center of a dipole consisting of charges + and - q separated by distance s. The charge is located in the plane that bisects the dipole. At this instant, what are (a) the force(magnitude and direction) and (b) the magnitude of the...

Homework Statement Show that the force between two aligned permanent dipoles, a distance r apart, is attractive and varies as r^{-4} Length of dipole to be taken as d.Homework Equations None provided. The Attempt at a Solution I'm completely lost here and have no idea where to begin. My...

Homework Statement See figure attached for the problem statement. Homework Equations The Attempt at a Solution I'm having some trouble getting started... How should I start to derive this result? Should I focus on one dipole with respect to the point P and then proceed...

Homework Statement A dipole p is directed in the positive z direction at the origin. The force on a dipole p in an electric field E is F=(p\cdot\nabla)E If a second dipole is placed at (r, \theta), by what factor must r increase – in terms of p, \theta and r – so that the net force between...

I just want to verify that the dipole moment \vec{m} in the presence of external magnetic field \vec{B} will line up in the the same direction and parallel with the external field. This is according to the right hand rule that if magnetic field is the direction of the thumb, the current will...

I'm taking an advanced thermodynamics course (its a pain!) anyways, we're studying intermolecular forces and how based on these forces, we can determine thermodynamic properties of pure components or mixtures, by linking them with statistical mechanics. my question is, how do you determine...

If you take 2 .5" x .5" cylinder neodymium magnets, and attach them sideways with N of first closest to the S of the 2nd and vice versa, they are attracted. However, when one is held stationary, and the other is rotated around, its seems that there is a perpendicular magnetic field that...

Homework Statement Arrange two electric dipoles with dipole moments qd nose to tail at a distance r (r >> d) along a line including their axis. Use Coulomb's law to show that the force between them varies as r4. Homework Equations The Attempt at a Solution So in my first...

My lecturer writes the following in his lecture notes: “Van der Waal’s : Fluctuating dipole of molecules induces dipoles in molecules or other- wise neutral atoms (eg noble gases)” Does a fluctuating dipole refer to a dipole that is changing its orientation in space? How causes a dipole...

Homework Statement An point electric dipole is located a vertical distance h above an infinite plane. What is the horizontal distance d from the dipole such that the electric field is zero at the horizontal distance d from the point dipole? Homework Equations...

Homework Statement Two dipoles as in pic below a distance r apart, find the torque applied to each dipole due to the other. \uparrow1 ------------2\rightarrow Homework Equations \itshape \vec{p}=p(cos\:\theta \hat{r}-sin\:\theta\hat{\theta}) \itshape...

By "static" in this thread, I mean the charge and current density is constant in time (so things can be moving, but the distribution cannot). We can build an arbitrary eletrostatic field with a "eletric monopole" density. Since Del.B=0, can we build an arbitrary magnetostatic field with just...

People say U for a magnetic dipole is -m . B But why can magnetic dipoles have potential energy, if magnetic forces are not conservative? Thanks!

Ok, so I have two magnetic dipoles, both lie on the x-axis, pointing in the positive x direction, say at x = 0 and x = a. I am to find the force of attraction between the two dipoles using the equation F=grad(m*B), as well as by the equation F=2(pi)IRBcos(theta), where R is the radius of a loop...

Homework Statement The potential due to an electric dipole is V(r)=pcos(theta)/(4*PI*epsilon*r^2) Determine the direction of the electric field E at theta = 0 , 45, 90, 135 and 180 degrees? Homework Equations The field of an electric dipole is given by Er =...

Consider 2 dipoles separated by a distance of atleast 2 light minutes or so . we can call the 1st dipole A . the distance btw the opposite charges is small so the field strength is weak same for the other dipole B . Now we increase the distance btw the charges in dipole A so the field...

Homework Statement IF THERE IS A MAXIMUM TORQUE WHEN THETA = 90 DEGREES BETWEEN ANGLE MADE BY THE DIPOLE VECTOR P AND THE ELECTRIC FIELD VECTOR E, WHY IS IT CONVENTION TO NOTE THE POTENTIAL ENERGY OF THE DIPOLE AT THETA = 90 DEGREES IS 0? SHOULDN'T THE POTENTIAL ENERGY AT THETA = 90...

Homework Statement Two opposite point charges of magnitude 1.90e-6 C are located near the origin. The positive charge is at (1.50, 1.50) mm and the negative charge is at (−1.50, −1.50) mm. What is the magnitude of the dipole moment vector for this pair of charges? Homework Equations p =...

Homework Statement I need to find force between two dipoles. I was thinking of finding F between all the four charges separately and then using superposition principle to get the net charge. but is there an easier way. Say, if I use the formula of E (dipole) for one dipole and multiply it...

If we have two charges, one at, say, 1C and one at, say, -1C, and they are separated by a distance of 1 meter, why is the voltage directly between them zero? A positive test charge will move towards the negative charge, and gain kinetic energy, but it started with no potential energy, and...

I'm trying to understand what electric dipoles, quadrupoles etc are. If i look for definitions of electric dipoles, they are given as pairs of point charges, yet no real examples are given.. "A point charge is an idealized model of a particle which has an electric charge. A point...

Homework Statement Two identical dipoles, each of charge q and separation a, are a distance x apart, as shown in Fig. By considering forces between pairs of charges in the different dipoles, calculate the net force between the dipoles. Show that, in the limit a<<x, the force has magnitude...

Consider an electric dipole whose dipole moment is oriented at angle theta with respect to the y axis. There is an external electric field of magnitude E pointing in the positive y direction. The positive and negative ends of the dipole have charges + q and - q, respectively, and the two...

Consider an electric dipole located in a region with an electric field of magnitude E pointing in the positive y direction. The positive and negative ends of the dipole have charges + q and - q, respectively, and the two charges are a distance D apart. The dipole has moment of inertia I about...

Dear everyone, I am researching genetic algorithms and at the moment I am trying to solve a problem how would magnetic particles (dipoles) orient themselves in a thin hollow sphere. Suppose that I have N magnetic dipoles placed in the sphere. There is no external magnetic field. The...

Help With Dipoles! I need some help on a question..how to set it up and solve it. Here is the question: Find the general expression for the electric field E(x,y) for a dipole charge +/- Q and length d oriented along the y-axis and symmetric about the x-axis. Thank you.

[b]1. The dipole moment of a peptide bond is 3.7 Debye in water. Assuming that a hydrogen bond is essentially a dipole-dipole interaction, estimate the energy of a hydrogen bond between two peptides in water and in the interior of a protein (neglect the competing interactions with the solvent)...

In the chapter on radiation (Chapter 11), Griffiths notes that an electric monopole does not radiate, but also that a point charge of electric dipole moment \mathbf{p} (t) = q \mathbf{d} (t) (where \mathbf{d} (t) is the instantaneous coordinate of the charge with respect to a fixed origin )...

A magnet has a N and a S pole to it, but if the electrons are always moving why are the N and S ends stationary instead of constantly changing/moving? Edit: I found this http://img235.imageshack.us/img235/3324/testra5.gif

If the electrons are small tiny dipoles, how do then they refuse them selfs? Thanks. I appreciate your help.

Suppose we have a gas of randomly oriented (and in random motion) electric dipoles. Obviously the dipoles do not behave as free particles. How do we describe it's properties? Can we define potential etc. ? I am looking for a solution without the large volume approximation. Is it possible to get...

i need to show that the mutual energy between two dioples p1 and p2 (not necessarily parallel to each other) is U=-\frac{p_1\cdot p_2}{|r|^3}-3\frac{(p_1\cdot r)(p_2\cdot r)}{|r|^5} where r is the vector from p_1 to p_2. (the p's are moments of diople). i tried using this equation: U=\int...

Homework Statement Griffiths offers this problem: two point dipoles p1 and p2 are given.They are r distance away and they are perpendicular.We are asked to find torue of p1 (about p1's centre) due to p2 and vice versa. Well, the situation is that I knoe it is =p cross E even I know the...

I have a figure showing two dipoles each having a Q and -Q charge with distance d separating the positive and negative of each dipole. The dipoles are then surrounded by multiple closed surfaces. I need to match fluxes of 8pikQ, 4pikQ, -8pikQ, - 4pikQ and 0 to these surfaces. Gauss' Law...

Difficulties with dipoles & point charges... Help would be appreciated a lot with the following problems: ~ A positive point charge +Q is at the origin, and a dipole of moment p is a distance r away (r>>L) and in the radial direction as shown below...

I'm having a little difficulty understanding the electric field generated from electric dipoles. As far as I know electric fields are generated on positive charges and terminated on negative charges. Since a dipole is a positive charge and a negative charge separated by a very small distance...